The invention relates to a device for damping torsional vibrations with at least two relatively rotatable elements of which one element is connectable with a motor and the other element is connectable with a gearbox and between the elements there is a torsion vibration damper which has energy accumulators and which counteracts the relative rotation between the two elements.
Devices of this kind are known for example through DE OS 39 09 892, DE OS 41 17 579, DE OS 41 17 580 and DE OS 41 17 584. With devices of this kind disc-like shaped sheet metal parts are very often used to hold and bias the energy accumulators which are provided between the two rotatable elements. In order to mount these energy accumulators the shaped sheet metal parts have shaped areas in which supporting or biasing regions are provided between the energy accumulators which are arranged in succession in the circumferential direction. The mountings for the energy accumulators are shaped so that guide regions are formed which are able to position the energy accumulators in the radial and/or in the axial direction. In many cases these radial and/or guide regions form axial indentations for the energy accumulators which are then housed at least in part in same.
As a result of the large material deformations or material displacements which are required in order to produce such disc-like or plate-like shaped sheet metal parts, stresses are generated in these component parts which cause distortion, deformation or curvature of the shaped sheet metal parts. It is therefore necessary in many cases to carry out secondary treatment on these shaped sheet metal parts, for example to carry out stock removing or thermal finishing treatment.
The object of the present invention is to configure disc-like or plate-like shaped sheet metal parts for devices of the kind mentioned at the beginning so that they have a high shape stability or shape resistance and tolerance to cold re-shaping steps, such as in particular pressing processes or drawing and imprinting operations.
According to the invention this is achieved in that in the extension region of the sections of the disc-like or plate-like shaped sheet metal part provided for mounting the energy accumulators, thus between the supporting or biasing regions for the energy accumulators, elongate impressed areas are created which extend in the circumferential direction at least in part over the length of the mounting sections for the energy accumulators which can be formed in particular by indentations. The measure according to the invention is particularly advantageous in the case of devices which have at most four circumferentially distributed energy accumulators which can be advantageously formed by coil compression springs. If only two energy accumulators are provided which each extend over 60 to 97% of half the circumference of the disc-like shaped sheet metal part and can be arranged diametrically opposite one another, the measure according to the invention has a particularly advantageous effect regarding the desired shape stability of the disc-like shaped sheet metal part. Disc like or plate-like shaped sheet metal parts of this kind have namely only two diametrically opposite biasing regions for the energy accumulators formed by impressed areas and producing stresses or inherent pressure strains in the shaped sheet metal part. These stresses cause the disc-like shaped sheet metal to be set up at a certain angle at the side of the impressed areas forming the supporting regions, so that an if only slight roof-shaped screen is formed. The sections of the disc-like shaped sheet metal part located at the side of the diametrically opposite biasing or supporting regions for the energy accumulators thus fold up together about a small angle like a book. By introducing elongate impressed areas according to the invention in the circumferential direction between the supporting regions for the energy accumulators, stresses such as in particular inherent pressure stresses are likewise built up in the material and counteract the stresses which are produced by imprinting the supporting regions. Distortion or a roof-shaped formation of the disc-like shaped sheet metal part can thereby be avoided, or at least reduced to an acceptable level
The impressed areas can be formed and shaped in a particularly advantageous way so that they mainly create material displacements, thus an internal flow of the material. Advantageously a compression of the material can take place and furthermore cold-solidification can also occur. Through the design of a disc like or plate-like shaped sheet metal part according to the invention it is also possible to guarantee a greater stability or stiffness of the component part. Since the corresponding component part can be made overall to keep within its dimensions or with substantially smaller shape tolerances, in many cases secondary finishing, such as for example stock-removing or rolling is no longer necessary.
In a particularly advantageous way the elongate impressed areas can be created in the sheet metal so that they cause a reduction in the material thickness of the shaped sheet metal part compared with the thickness of the regions adjoining the impressed areas. Advantageously the elongate impressed areas are formed in the sheet metal so that they form or produce no or practically no axial material projection on the side of the shaped sheet metal part facing away from same.
It can be particularly advantageous if the elongate impressed areas are introduced from the same side of the shaped sheet metal part as the molded areas, such as in particular the axial indentations for mounting the energy accumulators. With a design of this kind the elongate or swage-like impressed areas can thus change directly into indentations or areas for mounting and guiding the energy accumulators. It can be particularly advantageous it the elongate impressed areas extend at least over 30% of the angular extension of the energy accumulators or indentations. The length of the impressed areas can thereby amount to 0.3 to 0.95 times the angular extension of the energy accumulators. The radial width of the elongate indentations can be in the order of from 10 to 30% of the external circumference of the energy accumulators which are to be mounted. Advantageously the elongate indentations can be configured so that their maximum impressed depth amounts to 10 to 30% of the thickness originally present in the region of the sections of the shaped sheet metal part adjoining the impressed areas. Although it can be advantageous if the elongate impressed areas have the same depth over practically their entire extension, in many cases it can also be expedient if these impressed areas or the base of these impressed areas have a path of changing depth. Viewed in cross-section the impressed areas can thereby be U-shaped, V-shaped, curved or another shape. It can also be expedient if several elongate impressed areas are formed in the shaped sheet metal part extending parallel to each other.
In order to produce and maintain the shape of a shaped sheet metal part according to the invention it can be particularly advantageous if in the region of a mounting or indentation for an energy accumulator there is a single impressed area. In many cases however it can also be expedient if in the region of a mounting or indentation of this kind there are several sector-shaped impressed areas arranged in succession in the circumferential direction.
In a particularly advantageous way the device according to the invention for damping torsional vibrations can be a constituent part of a so-called twin-mass flywheel or can even form same. A shaped sheet metal part designed according to the invention can thereby form a constituent part of at least one of the flywheel masses. Advantageously the device can have two relatively rotatable flywheel masses of which one is connectable to an output shaft of an internal combustion engine and the other is connectable to a gearbox, preferably through a friction clutch. The two flywheel masses can thereby be positioned rotatable coaxial with each other through a bearing.
In a particularly advantageous way the shaped sheet metal part designed according to the invention can have a flange-like radially aligned region which has radially inside an axial integral shoulder for mounting the bearing. This axial shoulder can be produced by flow pressing. For mounting the bearing this axial shoulder must have a very high precision with regard to its roundness. This is particularly important when a slide bearing is used to form the bearing. By introducing the elongate impressed areas according to the invention in the region of the radially outer spring mountings a significantly narrower tolerance is obtained with regard to the roundness of the axial shoulder. This is due to the fact that as a result of introducing the elongate impressed areas according to the invention the shaped sheet metal part cannot become distorted so that an oval deformation of the axial shoulder on leaving the imprinting tool is avoided or at least reduced to an acceptable measure. A comparison between the shaped sheet metal parts without the impressed areas according to the invention and those having the impressed areas according to the invention has shown that the non-roundness in the region of the axial shoulder or bearing seat can be reduced by 50%. Thus a shaped sheet metal part without the impressed areas according to the invention would have an out-of-roundness of 0.04 mm, whilst a shaped sheet metal part provided with the impressed areas according to the invention would only have an out-of-roundness of less than 0.01 mm. Too much non-roundness in the region of the bearing seat or axial shoulder causes on the one hand great difficulty in mounting the bearing and on the other increased friction or increased torsional resistance inside the bearing. This can lead in the case of twin-mass flywheels to problems occurring at least during the operation in the idling area of the combustion engine equipped with such a twin-mass flywheel.
Advantageously the disc-like or plate-like shaped sheet metal part can be connected directly to the output shaft of an internal combustion engine. To this end this shaped sheet metal part can have screw holes which are arranged on a larger diameter than the external diameter of the axial shoulder or bearing.
The regions of the shaped sheet metal part forming the mountings or indentations for the energy accumulators can advantageously form an axial shoulder on which a radially inwardly extending wall is fixed which together with this shaped sheet metal part defines a ring-shaped chamber which is sealed at least radially on the outside and which extends at least over the radial extension of the energy accumulators or the mountings for same. Advantageously this wall can also be formed as a shaped sheet metal part and can have mounting areas or indentations and biasing areas for the energy accumulators. If the additional wall is formed by a shaped sheet metal part then it is expedient if this also has elongate impressed areas which can he formed and arranged like those of the disc like or plate-like shaped sheet metal part.
In order to compress the energy accumulators which are mounted in the ring-shaped chamber a flange body can advantageously be provided which extends at least with biasing regions for the energy accumulators from radially inside into the ring-shaped chamber and which is in driving connection by radially further inner areas to the other flywheel mass mounted on the gearbox side. This drive connection can be produced either through a rigid connection, through a force-locking connection, such as for example a slip clutch, or however through a further rotationally elastic damper.
With regard to the basic shaping, arrangement and functioning of a shaped sheet metal part designed according to the invention, reference is made to the prior art already mentioned whose contents are to be regarded expressly as integrated in the present application, so that a detailed description of different devices for damping torsional vibrations can be omitted from the present application.